Mineralogical variation and paragenesis of the mineralisation and alteration at the Neoproterozoic Rosh Pinah Zn-Pb-Ag deposit, Namibia

Significant alteration has affected the rocks at the Rosh Pinah Zn-Pb-Ag deposit. Silicification has previously been identified as the major alteration style that destroyed many of the original textures in the host rocks to the deposit. However, the timing of silicification and the possible presence of other significant alteration events have not been properly constrained, nor have the age and genetic relationships between alteration and mineralisation events. This study combines transmitted and reflected light petrography, scanning electron microscopy, "hot" cathodoluminescence, laser ablation ICP MS and whole rock geochemistry to determine the paragenetic sequence of alteration/mineralisation events at Rosh Pinah. Dominantly replacive pyrite, sphalerite, galena, and minor chalcopyrite, are hosted within weakly metamorphosed altered argillites, siltstones, carbonate rocks and volcanic rocks collectively known at the mine as the Ore Equivalent Horizon. This interval displays variable alteration, with the fine siliciclastic units (argillite and siltstones) affected mainly by silicification and barium enrichment of both detrital and authigenic feldspars and phyllosilicates. Carbonate rocks were affected by multiple dolomitization events.